This invention is related to an anti-static resin composition particularly transparent resins compositions comprising a thermoplastic polymer and a halogenated carbon sulfonic acid salt of a polysubstituted phosphonium compound and to a halogenated carbon sulfonic acid salt of a polysubstituted phosphonium compound.
Many polymers or blends of polymers are relatively non-conductive. As such, this can result in a static charge build-up during processing and use of the polymer. The charged polymer molded parts can attract dust, which are small particles, and can thus interfere with a smooth surface appearance. The attracted particles to the surface of a molded article may also cause a decrease in the transparency of the article. In addition, the electrostatic charge can be a serious obstacle in the production process of such polymers. In the past, electrically conductive agents such as carbon and metallic particles or surfactants were used in various attempts to reduce electrostatic charges of synthetic macromolecular materials by mixing them internally together or by coating the material with an agent. These methods employing electrically conductive agents are not generally feasible for many reasons such as the large amount of agents which must be usually used, the difficulty in adding them to the material, the difficulty in obtaining a transparent product or retention of mechanical and rheological properties, if that is the case, and the high cost of such conductive agents. Thus, these agents can be used only in limited situations.
Anti-static agents are materials which are added to polymers to reduce their tendency to acquire an electrostatic charge, or when a charge is present, these anti-static agents promote the dissipation of such a charge. The anti-static agents are usually hydrophilic or ionic in nature. When present on the surface of polymeric materials, they facilitate the transfer of electrons and thus eliminate the build up of a static charge. Anti-static agents have been applied in two ways. One method uses external anti-static agents that are applied by spraying the surface or dipping of the polymeric material. The second method uses internal anti-static agents, which are added to the polymer before processing. It is necessary for anti-static agents applied in this manner that they are thermally stable and able to migrate to the surface during processing.
Since there are many anti-static agents having surfactants as their main constituent, appropriate ones may be selected therefrom according to the situation. In fact, many of the types to be internally added have been considered and tried. When used as an internally-applied anti-static agent, however, anionic surfactants are difficult to handle because they are inferior in compatibility and uniform dispersibility and tend to decompose or deteriorate when heated. Cationic surfactants containing quarternary nitrogen in their molecules and amphoteric surfactants, on the other hand, can be used only in limited situations because they are extremely poor in heat resistance, although their anti-static characteristics are good. As for non-ionic surfactants, they are relatively superior to the aforementioned ionic surfactants regarding compatibility with synthetic macromolecular materials, but tend to be weak in anti-static characteristics and their effects disappear with time at normal or high temperatures. Moreover, because of the limited thermal stability of these non-ionic surfactant anti-static agents, their use with engineering thermoplastic resins, such as aromatic polycarbonates, is also limited due to the temperatures at which such resins are processed. Thus, these types of surfactants adversely affect the optical properties of aromatic polycarbonates. Although metal salts of organic sulfonic acids have been reported, especially as internally applied anti-static agents for polycarbonates and polyester resins which are molded at high temperatures, they are not sufficient in compatibility with resins or heat resistance one adverse consequence of insufficient compatibility is that transparency characteristics of certain macromolecular materials such as polycarbonates are lost with such anti-static agents. There has also been a report of using phosphonium salts or organic sulfonic acids having halogen substituent as a flame retardant (U.S. Pat. No. 4,093,589), but they are not to be expected to serve as anti-static agents as well.
Another patent discloses reducing the static charge on polycarbonate resins. This is U.S. Pat. No. 4,943,380, which discloses an anti-static composition containing 90-99.9 weight % of polycarbonate and 0.1-10 weight % of a heat resistant phosphonium sulfonate having the general formula: 
where R is a straight or branched chain alkyl group having from 1 to 18 carbon atoms; R1, R2 and R3 are the same, each being an aliphatic hydrocarbon with 1-18 carbon atoms or an aromatic hydrocarbon group; and R4 is a hydrogen group with 1-18 carbon atoms. The corresponding cationic surfactants containing quarternary nitrogen in their molecules can only be used in limited situations, because they are extremely poor in heat resistance although their anti-static characteristics are good (U.S. Pat. No. 5,468,973).
It is, therefore, an object of this invention to provide an anti-static resin composition comprising such polymers as polycarbonate, polyetherimide, polyester, polyphenylene ether/polystyrene blends, polyamides, polyketones, acrylonitrile-butadiene-styrene (ABS) or blends of these polymers or blends thereof with other materials or polymers, and a heat resistant anti-static material with which the aforementioned problems of conventional agents can be eliminated.
It is another object of this invention to provide a new anti-static agent which can be internally added to a synthetic resin preferably having transparent characteristics in the molded state without adversely affecting the transparency and mechanical properties of the molded article. However, this invention is not limited to transparent thermoplastics since anti-static requirements are also applicable to pigmented or translucent molded thermoplastic polymer articles.
Briefly, it has been discovered, according to the present invention, that relatively small quantities of certain heat resistant substituted phosphonium salts of medium and short chain halogenated fluorocarbon sulfonic acids of about 0.05-10 wt %, preferably about 0.2-1.5 wt %, and more particularly about 0.5-1.5 wt %, can be used as internal anti-static agents in polycarbonate, polyetherimide, polyester, polyphenylene ether/polystyrene blends, polyamides, polyketones, ABS or blends of these polymer resins of about 90-99.95 wt %, preferably about 98.5-99.8 wt % and more particularly about 98.5-99.5 wt %, the weight % based on the total weight of polymer and additive. In general, the substituted phosphonium salts of the medium and short chain sulfonic acids have the general formula: 
wherein X is independently selected from halogen or hydrogen provided that at least one (1) X is halogen; n, m and p are integers from 0 to 12; and Y is zero  a single bond or a heterocyclic atom, other than carbon, of an atomic ring and is either  heteroatom such as nitrogen, oxygen, sulfur, selenium, phosphorus, arsenic, and the like; R1, R2, and R3 are the same, each having an aliphatic hydrocarbon radical with 1-8 carbon atoms or an aromatic hydrocarbon radical of 6-12 carbon atoms and R4 is a hydrocarbon radical with 1-18 carbon atoms. The halogens may be independently selected from bromine, chlorine, fluorine and iodine. Preferably, the halogen is fluorine.
The phosphonium sulfonate is preferably fluorinated phosphonium sulfonate and is composed of a fluorocarbon containing an organic sulfonate anion and an organic phosphonium cation. Examples of such organic sulfonate anions include perfluoro methane sulfonate, perfluoro butane sulfonate, perfluoro hexane sulfonate, perfluoro heptane sulfonate and perfluoro octane sulfonate. Examples of the aforementioned phosphonium cation include aliphatic phosphonium such as tetramethyl phosphonium, tetraethyl phosphonium, tetrabutyl phosphonium, triethylmethyl phosphonium, tributylmethyl phosphonium, tributylethyl phosphonium, trioctylmethyl phosphonium, trimethylbutyl phosphonium trimethyloctyl phosphonium, trimethyllauryl phosphonium, trimethylstearyl phosphonium, triethyloctyl phosphonium and aromatic phosphoniums such as tetraphenyl phosphonium, triphenylmethyl phosphonium, triphenylbenzyl phosphonium, tributylbenzyl phosphonium.
The fluorinated phosphonium sulfonate of the present invention can be obtained by any combination of any of these organic sulfonate anions and organic cations but this invention is not limited by the examples given above. Fluorinated phosphonium sulfonate may be produced in a very pure form by mixing the corresponding sulfonic acid and the quarternary phosphonium hydroxide in a solvent mixture followed by evaporation of the solvent mixture. Tetrabutyl phosphonium perfluoro butane sulfonate, for example, can be produced with a yield of about 95% by placing 98.6 g. of perfluoro butane sulfonic acid, 200 ml. of a 40 wt. % solution of tetrabutyl phosphonium hydroxide and a 500 ml of a solvent mixture in a flask, stirring the mixture for one hour at room temperature, isolating phosphonium sulfonate which separates as an oily layer, washing it with 100 ml of water, followed by evaporation of the solvents using a vacuum pump.
As stated the preferred phosphonium sulfonate employed herein is a fluorinated phosphonium sulfonate having the general formula: 
wherein F is fluorine; n is an integer of from 1-12, S is sulfur; R1, R2 and R3 are the same, each having an aliphatic hydrocarbon radical of 1-8 carbon atoms or an aromatic hydrocarbon radical of 6-12 carbon atoms and R4 is a hydrocarbon radical of 1-18 carbon atoms. Anti-static compositions comprising fluorinated phosphonium sulfonate shown by formula (3) having the principle component thereof can be used in many different ways to make use of their anti-static and compatibility characteristics and heat resistance in providing such anti-static characteristics to polycarbonate, polyetherimide, polyester, polyphenylene ether/polystyrene blends, polyamides, polyketones, ABS or blends of these polymers. The phosphonium fluorocarbon sulfonate salts to this invention are low melting semi-solid materials, and as such, they can be handled as a molten liquid. Some embodiments in the present invention are solid crystalline materials at room temperature (15-25xc2x0 C.) and are easy to weigh, handle, and add to the polycarbonate, polyetherimide, polyester, polyphenylene ether/polystyrene blends, polyamides, polyketones, ABS or blends of these polymers.
A common way to practice this method is to add the agent directly and to mix it at the time of polymer production or fabrication. It can be processed by conventional means, including extrusion, injection, moulding, compression moulding or casting. The quantity of the phosphonium fluorocarbon sulfonate salt added to polycarbonate, polyetherimide, polyester, polyphenylene ether/polystyrene blends, polyamides, polyketones, ABS or blends of these polymers is an amount effective to reduce or eliminate a static charge and can be varied over a range. It has been found that if too little of the anti-static substituted phosphonium fluorocarbon sulfonate salt is added to the resin, there still may be a tendency for static charge to build up on the article made of the resin. If the loadings of the anti-static additive become too high, the addition of these quantities is uneconomical, and at some level it may begin adversely to affect other properties of the resin. For example, in order to obtain a favorable result by such an internal application method in transparent polycarbonate grades, it is preferable to add an agent of the present invention at the rate of 0.1-1.5 wt % with respect to the molding composition and it is even more preferable to do so at the rate of 0.4-0.8 wt %. Antistats of the present invention are more strongly resistant against heat and can be added in lower quantities than the conventional ionic surfactants, e.g. phosphonium alkyl sulfonates, and the resin compositions have good transparency and mechanical properties.
This invention can be further described by means of the following Examples. It should be understood, however, that this invention shall in no way be restricted by these Examples. In the Examples where comments are in terms of percent, they are percent by weight.
The following two test procedures were employed to analyze samples for anti-static behavior. These were the Dust Attraction test, static charge measurements and the surface resistivity by static charge measurement.
Dust Attraction Test
Dust attraction in transparent polycarbonate articles was developed. In this procedure, several color plaques are put in an exicator which is saturated with an in situ prepared NH4Cl dust for 60 minutes. The dust chamber is equilibrated for 1 hour before the samples are inserted. After 1 hour, the samples are removed and pictures of the color plaques together with the reference material are made using a projector lamp as a light source. The plaques are visually analyzed for appearance against a polycarbonate reference plaque containing no anti-static agent.
Surface Resistivity
Surface resistivity measurements were made at 55xc2x0 C. because at room temperature resistivity values have values in the range of 1017-1018 Ohm, in which range accurate results are difficult to obtain. Therefore, at a temperature of 55xc2x0 C., resistivity values have values in the range of 1013-1014 Ohm.
In addition to the above tests, the following tests were also conducted: